Material page for countersunk washers (90° seat) in A2 Stainless Steel (ISO 3506 group A2 (304 / 1.4301), commonly supplied A2-70). The sizes below are the ones we supply; there is no published dimensional standard for this article, so the table rather than a standard number is what to quote. Corrosion behaviour is good general corrosion resistance and the service range is approx. -200 °C to +400 °C, subject to the property class and the joint.
Why Choose A2 Stainless Steel for Countersunk Washers (90° Seat)
The most common stainless group for indoor and general outdoor fasteners. For countersunk washers (90° seat), this matters when good general corrosion resistance is the primary requirement.
Mechanical & Physical Properties
| Grade designation | ISO 3506 group A2 (304 / 1.4301), commonly supplied A2-70 |
|---|---|
| Magnetic response | Largely non-magnetic |
| Service temperature | approx. -200 °C to +400 °C, subject to the property class and the joint |
| Corrosion characteristic | Good general corrosion resistance |
Corrosion Behavior in Service
A2 (304) gives excellent atmospheric and most-water corrosion resistance and is the most common stainless for Countersunk Washers (90° Seat) in indoor and general outdoor service. In chloride-bearing environments (marine air, road salt, swimming pools) consider stepping up to A4 (316).
Comparable Grades
For Countersunk Washers (90° Seat), the alternative stainless grade is A4 (316). Choose A2 (304) for general use and A4 (316) wherever chlorides are present; the molybdenum in A4 is the whole difference. Remember that stainless is the corrosion answer, not the strength answer — for load, look at class 8.8 or 10.9 instead.
Using Stainless Fasteners in Aluminum
Stainless steel is more noble than aluminum, so with an electrolyte present — rain, condensation, salt spray — the aluminum becomes the anode and corrodes at the joint. Area ratio decides how bad it gets: a small stainless fastener in a large aluminum section is normally acceptable, a large stainless fastener in thin aluminum is not. Where the joint gets wet, isolate the metals with a coated or nylon washer and a sealant, or specify an aluminum or coated fastener instead.
Sizes of Countersunk Washers (90° Seat) Available in A2 Stainless Steel
| For screw size | Inner diameter d1 (mm) | Outer diameter d2 (mm) | Thickness t (mm) | Countersink angle | Material | Finish | Note |
|---|---|---|---|---|---|---|---|
| M4 | 4.3 | 11.0 | 2.0 | 90 | Stainless A2 | Passivated | Matches ISO 7046 heads |
| M5 | 5.3 | 13.0 | 2.5 | 90 | Stainless A2 | Passivated | Matches ISO 7046 heads |
| M6 | 6.4 | 16.0 | 3.0 | 90 | Stainless A2 | Passivated | Matches ISO 7046 heads |
| M8 | 8.4 | 20.0 | 3.5 | 90 | Stainless A2 | Passivated | Matches ISO 10642 heads |
| M10 | 10.5 | 24.0 | 4.0 | 90 | Steel | Zinc plated | Matches ISO 10642 heads |
Dimensions are independent of the material: every size above is available in A2 Stainless Steel.
Custom manufacturing · Made to drawing
Need this washer in a grade that is not listed?
A2 Stainless Steel is one of the grades the catalog describes. Bore and outside diameter are set by the joint rather than by the bolt, which is why an off-table size is so often the right answer. Made by stamping or punching.
Minimum order from 2,000 pieces; samples within 7 days of drawing approval.
